The present invention relates to a heat insulating material having an extremely low thermal conductivity in a vacuum and flexibility and in more detail to a heat insulating material suitable for insulating a body of a space shuttle, a rocket, etc.
Heretofore, as this kind of heat insulating material, a heat insulating structure has been proposed in JP-A-Sho 59-106954, in which a core member consisting of accumulated heat resisting inorganic fiber, which is not deformed at sewing, is put between a high temperature side skin member and a low temperature side skin member made of heat resisting inorganic fiber textile and these three members are tied in one body by sewing, using heat resisting inorganic fiber thread.
However such a heat insulating structure has disadvantages not only that seams are easily displaced so that it is not possible to prevent scattering of material constructing the core member but also that fiber constructing the skin members comes often untied so that the structure is easily destroyed, because side wall parts of the structure are only sewn by using sewing thread.
In addition, since the core member consisting of accumulated heat resisting inorganic fiber has a relatively large thermal conductivity in vacuum and the thermal conductivity is further increased by influences of sewing thread and pinholes made at sewing, it is necessary that the thickness for insulation is great and therefore it has a drawback that the heat insulating material should be heavy.
The present invention has been made in order to remove the above-mentioned disadvantages of the heat insulating structure and a heat insulating material, in which a core member consisting of accumulated heat resisting inorganic fiber is put between a high temperature side skin member and a low temperature side skin member made of heat resisting inorganic fiber textile and these three members are made in one body, according to the present invention, is characterized in that side wall parts of the core material is covered with the high temperature skin member and that the core member consists of 100 weight parts of heat resisting inorganic fiber and 15 to 50 weight parts of SiC powder and/or SiC whisker.